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[v2 2/7] x86/mpx: Fail when implicit zero-displacement is used along with R/EBP

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Section 2.2.1.2 of the Intel 64 and IA-32 Architectures Software
Developer's Manual volume 2A states that when memory addressing with no
explicit displacement (i.e, mod part of ModR/M is 0), a SIB byte is used
and the base of the SIB byte points to (R/EBP) (i.e., base = 5), an
explicit displacement of 0 must be used.

Make the address decoder to return -EINVAL in such a case.

Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Adam Buchbinder <adam.buchbinder@gmail.com>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Qiaowei Ren <qiaowei.ren@intel.com>
Cc: Ravi V. Shankar <ravi.v.shankar@intel.com>
Cc: x86@kernel.org
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
---
 arch/x86/mm/mpx.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/x86/mm/mpx.c b/arch/x86/mm/mpx.c
index 6a75a75..71681d0 100644
--- a/arch/x86/mm/mpx.c
+++ b/arch/x86/mm/mpx.c
@@ -120,6 +120,13 @@ static int get_reg_offset(struct insn *insn, struct pt_regs *regs,
 
 	case REG_TYPE_BASE:
 		regno = X86_SIB_BASE(insn->sib.value);
+		if (regno == 5 && X86_MODRM_RM(insn->modrm.value) == 0) {
+			WARN_ONCE(1, "An explicit displacement is required when %sBP used as SIB base.",
+				  (IS_ENABLED(CONFIG_X86_64) && insn->x86_64) ?
+				  "R13 or R" : "E");
+			return -EINVAL;
+		}
+
 		if (X86_REX_B(insn->rex_prefix.value))
 			regno += 8;
 		break;
-- 
2.9.3

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[v2 0/7] x86: enable User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-12-24 02:40 +0100
  [v2 5/7] x86: Add emulation code for UMIP instructions Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-12-24 02:40 +0100
    Re: [v2 5/7] x86: Add emulation code for UMIP instructions Andy Lutomirski <luto@amacapital.net> - 2016-12-24 03:20 +0100
      Re: [v2 5/7] x86: Add emulation code for UMIP instructions Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-12-28 01:40 +0100
        Re: [v2 5/7] x86: Add emulation code for UMIP instructions Andy Lutomirski <luto@amacapital.net> - 2016-12-28 01:50 +0100
          Re: [v2 5/7] x86: Add emulation code for UMIP instructions Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-12-30 06:30 +0100
            Re: [v2 5/7] x86: Add emulation code for UMIP instructions Andy Lutomirski <luto@amacapital.net> - 2016-12-31 03:10 +0100
    Re: [v2 5/7] x86: Add emulation code for UMIP instructions Masami Hiramatsu <mhiramat@kernel.org> - 2016-12-25 17:00 +0100
      Re: [v2 5/7] x86: Add emulation code for UMIP instructions Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-12-28 01:50 +0100
  [v2 3/7] x86/mpx, x86/insn: Relocate insn util functions to a new insn-utils Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-12-24 02:40 +0100
    Re: [v2 3/7] x86/mpx, x86/insn: Relocate insn util functions to a  new insn-utils kbuild test robot <lkp@intel.com> - 2016-12-24 03:40 +0100
    Re: [v2 3/7] x86/mpx, x86/insn: Relocate insn util functions to a  new insn-utils Masami Hiramatsu <mhiramat@kernel.org> - 2016-12-25 07:20 +0100
      Re: [v2 3/7] x86/mpx, x86/insn: Relocate insn util functions to a  new insn-utils Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-12-27 23:40 +0100
    Re: [v2 3/7] x86/mpx, x86/insn: Relocate insn util functions to a new  insn-utils Dave Hansen <dave.hansen@linux.intel.com> - 2017-01-03 17:50 +0100
  [v2 2/7] x86/mpx: Fail when implicit zero-displacement is used along with R/EBP Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-12-24 02:50 +0100
    Re: [v2 2/7] x86/mpx: Fail when implicit zero-displacement is used  along with R/EBP Andy Lutomirski <luto@amacapital.net> - 2016-12-24 03:00 +0100
      Re: [v2 2/7] x86/mpx: Fail when implicit zero-displacement is used  along with R/EBP Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-12-27 23:40 +0100
        Re: [v2 2/7] x86/mpx: Fail when implicit zero-displacement is used  along with R/EBP Dave Hansen <dave.hansen@linux.intel.com> - 2017-01-03 17:50 +0100

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